# C Program to Interchange Diagonals of a Matrix

How to write a C Program to Interchange Diagonals of a Matrix with an example?.

## C program to Interchange Diagonals of a Matrix Example

This program allows the user to enter the number of rows and columns of a Matrix. Next, we are going to interchange the diagonals of the given matrix using For Loop.

/* C program to interchange Diagonals of a Matrix */

#include<stdio.h>

int main()
{
int i, j, rows, columns, arr[10][10], temp;

printf("\n Please Enter Number of rows and columns  :  ");
scanf("%d %d", &i, &j);

printf("\n Please Enter the Matrix Elements \n");
for(rows = 0; rows < i; rows++)
{
for(columns = 0;columns < j;columns++)
{
scanf("%d", &arr[rows][columns]);
}
}

if(rows == columns)
{
for(rows = 0; rows < i; rows++)
{
temp = arr[rows][rows];
arr[rows][rows] = arr[rows][i - rows - 1];
arr[rows][i - rows - 1] = temp;
}

printf("\n Matrix Elemnts after Interchanging Diagonals are: \n");
for(rows = 0; rows < j; rows++)
{
for(columns = 0; columns < i; columns++)
{
printf("%d \t ", arr[rows][columns]);
}
printf("\n");
}
}
else
{
printf("\n The Matrix that you entered is Not a Square matrix" );
}

return 0;
}

In this Program, We declared single Two dimensional arrays Multiplication of size of 10 * 10. The below C Programming statements asks the User to enter the Matrix size (Number of rows and columns. For instance 2 Rows, 2 Columns = a[2][2] )

printf("\n Please Enter Number of rows and columns  :  ");
scanf("%d %d", &i, &j);

Next, we used for loop to iterate each cell present in a[2][2] matrix. Conditions inside for loop ((rows < i) and (columns < j)) will ensure the compiler, not to exceed the Matrix limit. Otherwise, the matrix will overflow. The scanf statement inside the for loop will store the user entered values in every individual array element such as a[0][0], a[0][1], …..

for(rows = 0; rows < i; rows++).
{
for(columns = 0; columns < j; columns++)
{
scanf("%d", &a[rows][columns]);
}
}

Next, we are using the If Else statement to check whether the given matrix is a Square matrix or Not. If it is True, then the compiler will interchange the diagonals. Otherwise, it will print a message present in else block.

for(rows = 0; rows < i; rows++)
{
temp = arr[rows][rows];
arr[rows][rows] = arr[rows][i - rows - 1];
arr[rows][i - rows - 1] = temp;
}

Next, we used another for loop to print the array. The user inserted values for C Program to Interchange Diagonals of a Matrix are: a[3][3] = {{10, 20, 30}, { 40, 50, 60},{70, 80, 90}}

Row First Iteration: for(rows = 0; rows < 3; 0++)
The condition (0 < 3) is True.

Column First Iteration: for(columns = 0; 0 < 3; 0++)
The condition (columns < 3) is True.
temp = arr[rows][rows] = 10
arr[0][0] = arr[0][3 – 0 – 1] => arr[0][2]
arr[0][0] = 30
arr[0][3 – 0 – 1] => arr[0][2] = temp
arr[0][2] = 10
Do the same for the remaining iterations.

## C program to Interchange Diagonals of a Matrix Example 2

This C program for matrix diagonal interchange is same as above but this time we used functions concept to operate the code.

/* C program to interchange Diagonals of a Matrix */

#include<stdio.h>
void interchnage_Diagonals(int arr[10][10], int i, int j);

int main()
{
int i, j, rows, columns, arr[10][10], temp;

printf("\n Please Enter Number of rows and columns  :  ");
scanf("%d %d", &i, &j);

printf("\n Please Enter the Matrix Elements \n");
for(rows = 0; rows < i; rows++)
{
for(columns = 0;columns < j;columns++)
{
scanf("%d", &arr[rows][columns]);
}
}

if(rows == columns)
{
interchnage_Diagonals(arr, i, j);
}
else
{
printf("\n The Matrix that you entered is Not a Square matrix" );
}

return 0;
}

void interchnage_Diagonals(int arr[10][10], int i, int j)
{
int rows, columns, temp;
for(rows = 0; rows < i; rows++)
{
temp = arr[rows][rows];
arr[rows][rows] = arr[rows][i - rows - 1];
arr[rows][i - rows - 1] = temp;
}

printf("\n Matrix Elemnts after Interchanging Diagonals are: \n");
for(rows = 0; rows < j; rows++)
{
for(columns = 0; columns < i; columns++)
{
printf("%d \t ", arr[rows][columns]);
}
printf("\n");
}
}

C matrix Diagonal interchange output

Please Enter Number of rows and columns  :  2 2

10 20
30 40

Matrix Elemnts after Interchanging Diagonals are:
20 	 10
40 	 30